Structurally Ordered Intermetallic Cobalt Stannide Nanocrystals for High‐Performance Electrocatalytic Overall Water‐Splitting

Abstract

The synthesis of structurally ordered non-noble intermetallic cobalt stannide (CoSn 2 )n anocrystals and their utilization for high-performance electrocatalytic overall watersplitting is presented. The structurally and electronically beneficial properties of the tetragonal CoSn 2 exhibit ac onsiderably low overpotential for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on fluorinedoped tin oxide (FTO) and Ni foam (NF). Loss of Sn from the crystal lattices and oxidation of Co under strongly alkaline conditions furnishes highly disordered amorphous active CoO x (H), the catalytically active structure for OER. The Co 0 atoms in the CoSn 2 act as active sites for HER and the presence of Sn provides efficient electrical conductivity.T his intermetallic phase is an ovel type of cost-effective and competitive bifunctional electrocatalysts and predestinated for overall water-splitting devices:At wo-electrode electrolyzer with CoSn 2 on NF delivers ac ell voltage of merely 1.55 Va t 10 mA cm À2 maintaining long-term stability.Intermetallic nanocrystals are considered to be an important class of nanomaterials in the field of superconductivity, ferromagnetism, thermoelectricity,s hape-memory effects, and catalysis owing to their intriguing chemical and physical properties. [1] Recently,i ntermetallic compounds have gained enormous attention in heterogeneous catalysis by virtue of their unusual and attractive crystallographic and electronic properties. [2] It has been shown that the extent of atomic ordering and the relative concentration of both metals drastically influence the overall reactivity efficiency. The recent development of structurally ordered intermetallic materials based on noble metals (Pt, Pd) and early transition metals (Fe, Co,N i) have been successfully used for efficient oxygen reduction reaction (ORR) and HER. Intermetallic compounds containing non-noble metals (main group and transition metals) were also shown to be potential candidates for application in data storage,m agnetic materials,e lectronics,a nd sensors to electrodes in rechargeable batteries. [3] However,t he geometric and electronic influence of such materials for the energy conversion and storage applications are still scarcely investigated.As acentral part for asustainable realization of renewable energy conversion, the development of inexpensive materials for technologies capable of electrochemical water-splitting into hydrogen and oxygen in an economically viable way is highly desired. [4] Currently,n oble-metal-based materials (Pt, RuO 2, and IrO 2 )have been considered as the state-of-the-art electrocatalysts for HER and OER;however,relatively high costs and scarcity of the materials greatly stint their widespread industrial applications. [5] Recently,h igh-performance bifunctional OER and HER electrocatalysts based on nonnoble transition-metal oxides/hydroxides, [6] carbonate/ hydroxides, [7] chalcogenides, [8] phosphides, [9] borides, [10] phosphates, [11] and phosphite [12] functioning in ac ommon elect...

Boosting Water Oxidation through In Situ Electroconversion of Manganese Gallide: An Intermetallic Precursor Approach

“…[19] Interestingly,t he higher oxidation states of Mn in comparison to XANES suggest the unavoidable air oxidation at the surface (XPS is surface sensitive) of the particles,w hich is typical for intermetallics. [14] In Ga 2p, the binding energy of 1116.4 eV attained for Ga 2p 3/2 is very similar to that of elemental Ga (1116.4 eV) and the second peak observed at the binding energy of 1118.2 eV could be corroborated with Ga bonded to an oxo species due to surface passivation. [20] As intermetallic MnGa 4 maintains metallic character,M nm etal (cubic, I-43m,N o.…”

Stannites – A New Promising Class of Durable Electrocatalysts for Efficient Water Oxidation

“…[10][11][12][13][14][15] Bi-and multi-nuclear-TM (pre)catalysts have proven to be superior to mononuclear ones, as the variation of the metal composition enables the tuning of the intrinsic properties affecting the OER. [16,17] In this regard, it has been shown that an multinuclear assembling of metals helps to vary adsorption energies [2,18] and can afford higher stabilities, [19][20][21] conductivities [22][23][24] and surface areas [25,26] of OER catalysts.…”

Steigerung der Wasseroxidation durch In‐situ‐Elektrokonversion eines Mangangallids: Ein intermetallischer Vorläuferansatz

“…Intermetallische Verbindungen besitzen einzigartige chemische, physikalische und elektronische Eigenschaften sowie unterschiedliche Kristallstrukturen . Die gute elektrische Leitfähigkeit und die höhere Adsorptionskapazität im Vergleich zu Oxiden prädestinieren intermetallische Verbindungen als geeignete Elektrokatalysatoren, insbesondere für die HER, wo die atomare Ordnung und die relative Konzentration beider Metalle den Wirkungsgrad drastisch beeinflussen; jedoch ist ihre Aktivität für die OER kaum erforscht. In dieser Arbeit präsentieren wir, dass Mangangallid (MnGa 4 ) ein neues Vorläufermaterial für die elektrokatalytische OER ist.…”

“…[19] Interessanterweise deutet die hçhere Oxidationsstufe von Mn im Vergleich zu der durch XANES bestimmten auf eine unvermeidbare Luftoxidation an der Oberfläche der Partikel hin (XPS ist oberflächensensitiv), die füri ntermetallische Verbindungen typisch ist. [14] In Ga 2p ist die fürGa2p 3 [21] Ausden C dl -Werten und der spezifischen Kapazitätdes Materials (C s ) pro Flächeneinheit wurde die ECSA berechnet, die 2.7 cm 2 fürMnGa 4 /NF und 1.54 cm 2 fürMn/NF betrug.Dies weist auf eine hçhere Dichte von aktiven Zentren sowie eine effizientere Adsorption und Übertragung von Reaktanten in MnGa 4 hin, was zu einer Verbesserung der elektrochemischen Reaktion führt. [21] Um Einblicke in die elektrokinetischen Eigenschaften der untersuchten OER-Katalysatoren zu erhalten, wurde die elektrochemische Impedanzspektroskopie (electrochemical impedance spectroscopy,E IS) eingesetzt, um detaillierte Informationen über Grenzflächenreaktionen zu erhalten (Abbildung 2b;A bbildung S28).…”